NPR: David Kestenbaum

David Kestenbaum is a correspondent for NPR, covering science, energy issues and, most recently, the global economy for NPR's multimedia project Planet Money. David has been a science correspondent for NPR since 1999. He came to journalism the usual way — by getting a Ph.D. in physics first.

In his years at NPR, David has covered science's discoveries and its darker side, including the Northeast blackout, the anthrax attacks and the collapse of the New Orleans levees. He has also reported on energy issues, particularly nuclear and climate change.

David has won awards from the American Association for the Advancement of Science, the American Physical Society and the Institute of Electrical and Electronics Engineers.

David worked briefly on the show This American Life, and set up a radio journalism program in Cambodia on a Fulbright fellowship. He also teaches a journalism class at Johns Hopkins University.

David holds a bachelor's of science degree in physics from Yale University and a doctorate in physics from Harvard University.

The online furniture company Wayfair is now one of the most shorted stocks. Our Planet Money team talks to its CEO about what it's like to be running a company when some investors are betting on your fall.

On January 1, 20 states raise their minimum wage and several states have additional increases planned in the coming months. Yesterday, we learned that Walmart will raise its base pay to $9 an hour this April.

The other day I went down to the little shop in the lobby of our building for a snack. I couldn't decide whether I wanted regular M&M's or Peanut Butter M&M's so I bought them both. On the way back upstairs to the office, I noticed something strange on the labels. Each had cost $1, but the pack of Peanut Butter M&M's was a very tiny bit lighter: 0.06 ounces lighter!

I wanted to know why, so I called a couple of experts and asked for their theories:

And now, 4,000 years of economic growth in seven minutes. This story comes, of course, from our Planet Money team. David Kestenbaum and Jacob Goldstein bring us the history of light and how the world came what it is today.

A couple years ago, Adrienne McAdory read that the organization that sets the rules for Web addresses was going to allow people to apply for new top-level domains. No longer would there be just the old top-level domains like .com and .gov. People could apply for any new top-level domain they wanted.

McAdory liked the idea, but it took her awhile to figure out the right domain.

"I was thinking about lifestyle," says McAdory. "My girlfriends and I just had incessant conversations about 'Oh, we're not married, can't find the right guy, blah, blah, blah.'"

In 1895, legislators in New York state decided to improve working conditions in what at the time could be a deadly profession: baking bread.

"Bakeries are actually extremely dangerous places to work," says Eric Rauchway, a historian at the University of California, Davis. "Because flour is such a fine particulate, if it gets to hang in the air it can catch fire and the whole room can go up in a sheet of flame."

This famous bet — between a biologist and an economist — was over population growth. It started three decades ago, but it helped set the tone for environmental debates that are still happening today.

The biologist at the heart of this bet was Paul Ehrlich at Stanford. He wrote a best-selling book in 1968 called The Population Bomb. It was so popular he appeared on The Tonight Show with Johnny Carson.

We recently published a story about how used clothes that get donated in the U.S. often wind up for sale in markets in Africa. As part of the story, we published some photos of used T-shirts we found in a couple of markets in Kenya.

Gavin Andresen is chief scientist at the Bitcoin Foundation. I first talked with him about Bitcoin, the virtual currency, back in 2011. I checked back in with him this week, because so much has been going on with Bitcoin lately.

Robert Shiller was surprised when he got the call telling him he'd won the Nobel Memorial Prize in economics — surprised that he'd won (of course), but also surprised that he was sharing the award with Eugene Fama.

"He and I seem to have very different views," Shiller told me. "It's like we're different religions."

What would happen if Congress doesn't raise the debt ceiling and the U.S. defaults on its debt later this month? The broad economic implications are unpredictable, but a default could cause huge trouble for the global economy.

But whatever happens to the global economy, one thing is clear: People all over the world who have loaned the U.S. government money won't get paid on time.

Well, it's happened. British scientist Peter Higgs has won a Nobel Prize for proposing the Higgs boson particle as part of a mechanism that explains how things in the universe came to have mass.

Higgs seems to be lying low today so far — a colleague told The New York Times that Higgs had "gone off by himself for a few days without saying where" and that a reporter seeking an interview recently had been "sent away with a flea in his ear."

Tuesday is a big day for Obamacare. The online marketplaces where people can shop for health insurance are supposed to open for business.

No one really knows who is going to sign up — not the Obama administration, not the insurance industry, not the president's critics. Yet the success of the law hangs on this question: Will the right mix of people sign up? In particular, will healthy people buy health insurance?